Security
How Vaultessa protects your files
Here's what happens to a file from the moment you add it, explained plainly first and then with the technical details.
In plain words
- Each folder has its own random key. It isn't made from your pattern, so a simple pattern doesn't mean a weak key.
- That key is locked twice: by your pattern, and by a key inside your phone's secure hardware that never leaves it. A copy of the app's storage on a computer is not enough to start guessing.
- Everything is encrypted: files, file names, file types and folder names.
- Nothing decrypted is saved. Photos, videos, music and documents are decrypted in memory while you look at them, never into a temporary file.
- Guessing gets slow. After 5 wrong patterns you wait 3 minutes, then 6, 12, 24 and so on.
- It locks when you leave. Home, the screen turning off, or a minute without touching it (you choose 10 to 60 seconds). Screenshots and the recent-apps preview are blocked.
Technical details
| Part | How it's done |
|---|---|
| Files | Tink streaming AES-256-GCM (HKDF, 1 MB segments), file ID bound as associated data |
| Names, file list | Tink AES-256-GCM, bound to the folder and purpose |
| Folder key | Random per folder, never derived from the pattern |
| Pattern | PBKDF2-HMAC-SHA256, calibrated to about 0.25 s, at least 150,000 iterations |
| Hardware layer | AES-256-GCM key in Android Keystore (StrongBox when the phone has it), non-exportable |
| Recovery code | 160 random bits, shown once as 32 characters |
| Backups | Encrypted parts plus a sealed, authenticated list of every part; any change is refused |
| Emergency folder | Hybrid public-key encryption (HPKE, X25519) so hiding needs no secret; the phrase unwraps the private key |
What Vaultessa can't protect against
No app can protect everything, and we'd rather you know the limits:
- A phone that's already compromised. Malware with full control of an unlocked phone can see what's on screen while a folder is open.
- Someone watching you draw. A pattern can be seen over your shoulder or read from smudges.
- Originals left behind. Vaultessa copies files in. Delete the originals and any cloud copies yourself.
- Knowing that Vaultessa is used. Anyone holding the phone can see the app is installed and that folders exist, though not what's in them.
- A lost recovery code. Without the pattern and the recovery code, a folder can't be opened by anyone, including us.
Vaultessa is built only on established, maintained cryptography (Google Tink and Android's own Keystore), with no home-made encryption. It hasn't had an independent security audit yet. When it has, the results will be published here.
Questions
Can Vaultessa see my files?
No. Vaultessa has no servers and never receives your files or keys. Everything is encrypted and stays on your phone.
What happens after too many wrong patterns?
After 5 wrong patterns Vaultessa makes you wait 3 minutes. Every further 5 doubles the wait, up to 24 hours. Changing the phone's clock doesn't shorten it.
Is an 8-dot pattern strong enough?
A pattern on its own is a weak secret, which is why Vaultessa never relies on it alone. The folder key is also locked by the phone's secure hardware, so guessing is only possible on your phone, under the waiting times.
Try Vaultessa
Free to start, with 2 pattern folders. No account, no ads, nothing in the cloud.
Get it on Google Play